Mates. Last week I drove my last trip back up our winter road which is now thawing and degenerating quickly. Total distance was about 360km of a combo of mud, slush, ice and snow. Thankfully the ground was still frozen, otherwise the going would have been a lot rougher than it was. About half-way back on the road, after going through quite a few large puddles of muddy, icy water my diff-lock light came on on the dash and with it the usual ABS light and warning horn when I accelerated above 20km/h. However, the diff lock was never engaged. I stopped and tested it multiple times and I could hear the vacuum engage and disengage when I toggled the diff-lock switch in the cab. Engaging and disengaging the diff lock, engaging and disengaging the 4wd high and low didn't make any difference, the indicator still stayed on.

I finally just ignored it and drove the rest of the way back and after a while the ABS warning tone went away, but the lights still stayed on. Got back to our home and gave the Patrol a good washing, but haven't been able to get the undercarriage really well yet. Lights are off for the most part now, but they still come back on occasionally.

What could have caused this and what do I need to check for? Does it just need a really good washing or do I need to track down a fault somewhere? I'm at a loss because everything functions as it should, just the indicator lights come on and off at random.